1. Field of the Invention
The present invention relates to a method for assembling a polishing head and an apparatus for detecting air leakage in the polishing head while assembling the same. More particularly, the present invention relates to a method for assembling a polishing head while inspecting each tube of the polishing head for air leakage and an apparatus suitable for performing the method.
2. Description of the Related Art
Semiconductor technology is making great strides as information media such as computers are becoming more widely used. In a functional aspect, a semiconductor device is required to be operated at a high speed with a large storage capacity. Accordingly, semiconductor technology is developed to improve the degree of integration, the reliability, and the response speed of semiconductor devices. Therefore, micro-processing techniques are governed by strict requirements in order to improve the degree of integration of semiconductor devices.
Among the micro-processing techniques for improving the degree of integration of semiconductor devices is a planarization technique. In the semiconductor manufacturing industry, chemical mechanical polishing (CMP), in which a wafer is directly polished, is primarily used as a planarization technique.
In order to evenly planarize a wafer using the CMP process, it is important that uniform pressure is applied to each part of the wafer during the CMP process. Accordingly, it is important to provide a proper polishing head, which grips the wafer (holds the wafer by applying suction to the wafer) thereby applying pressure to the wafer during the CMP process.
Specifically, an inner portion of the polishing head has a plurality of tubes used for air passage. A pneumatic pressure or a vacuum is supplied through the tubes. At this time, the wafer below the polishing head is pushed towards a polishing pad by the pneumatic pressure supplied to the polishing head, so that a contact-pressure between the wafer and the polishing pad increases. In addition, the wafer is gripped by suction at a lower portion of the polishing head by the vacuum supplied to the polishing head. However, if there is any air leakage in the tubes of the polishing head, the predetermined pneumatic pressure or the predetermined vacuum cannot be normally supplied to the polishing head. In such a case of air leakage in the tubes, the wafer is unevenly polished to do non-uniform pressure, or the wafer falls from the polishing head due to insufficient suction.
The prior art discloses a polishing device including a polishing head having an air line for controlling the operation of the polishing head and an air control system for controlling the polishing head. The air control system inspects for air leakage in the air line of the polishing head installed in the polishing device. In addition, the prior art discloses a polishing head capable of checking for the existence of a wafer by detecting a pressure variation.
The polishing head has to be periodically disassembled for cleaning or exchanging parts thereof. After being re-assembled, the polishing head is installed in the polishing device. If the polishing head is incorrectly assembled, the pneumatic pressure or the vacuum supplied to the polishing head leaks therefrom, so that the polishing head is unable to grip the wafer or the wafer does not receive a precise pressure. Therefore, after assembling the polishing head, testing the polishing head for the existence of air leakage is required. Only if the polishing head does not generate any air leakage can it be used in the CMP process.
The test method is as follows. Firstly, the assembled polishing head is installed in the polishing device. Then, the CMP process, in which a wafer is gripped by the polishing head, is carried out using a dummy wafer. Thereafter, a surface of the polished dummy wafer is inspected to detect scratches and particles formed thereon, thereby determining whether or not the dummy wafer is normally polished. Upon completion of the test, if the dummy wafer is normally polished, a wafer for manufacturing a semiconductor device is introduced into the polishing device equipped with the polishing head, and the CMP process is carried out with respect to the wafer.
If the dummy wafer is abnormally polished, a user separates the polishing head from the polishing device in order to disassemble and reassemble the polishing head. Then, after re-assembling the polishing head, the leakage test must again be carried out using a dummy wafer to test the polishing head. The leakage test takes about 6 hours. Since about 10% of assembled polishing heads have some air leakage, it is necessary to reassemble the polishing heads about 10% of the time, resulting in a marked reduction in production from the polishing device. Accordingly, productivity of the semiconductor device manufacturing equipment is also lowered.
In order to solve the problems mentioned above, it is a first feature of an embodiment of the present invention to provide a method for assembling a polishing head while inspecting the polishing head for air leakage.
A second feature of an embodiment of the present invention is to provide an apparatus for inspecting a polishing head for air leakage during assembly of the polishing head.
To provide the first feature of an embodiment of the present invention, the method for assembling a polishing head while inspecting for air leakage in the polishing head includes assembling an inner tube among disassembled parts of the polishing head, supplying a first pressure through a first pressure line to a first tube connected to the inner tube and inspecting for air leakage by determining if there is any variation in the first pressure in the first tube connected to the inner tube, assembling a membrane in a state that the inner tube is assembled, supplying a second pressure through a second pressure line to a second tube connected to the membrane and inspecting for air leakage by determining if there is any variation in the second pressure in the second tube connected to the membrane, supplying a first level of vacuum through a first vacuum line to the second tube connected to the membrane and inspecting for air leakage by determining if there is any variation in the level of vacuum in the second tube connected to the membrane, assembling a retainer ring in a state that the membrane is assembled, thereby completing an assembling of the polishing head, supplying a third pressure through a third pressure line to a third tube connected to the retainer ring and inspecting for air leakage by determining if there is any variation in the third pressure in the third tube connected to the retainer ring, and supplying a second level of vacuum through a second vacuum line to the third tube connected to the retainer ring and inspecting for air leakage by determining if there is any variation in the second level of vacuum in the third tube connected to the retainer ring.
Preferably, inspecting for air leakage is carried out by supplying a predetermined pressure or level of vacuum to a predetermined tube of the polishing head to be inspected while tubes that are not subject to inspection are closed, closing the predetermined pressure or vacuum line, through which the predetermined pressure or level of vacuum is supplied to the predetermined tube when the pressure or level of vacuum in the predetermined tube reaches the predetermined pressure or level of vacuum, determining if there is any variation in the pressure or level of vacuum in the predetermined tube after a predetermined period of time after closing the predetermined pressure or vacuum line, determining whether air leakage occurs by measuring any variation in the pressure or level of vacuum in the predetermined tube and comparing the variation in the pressure or level of vacuum with a predetermined pressure or level of vacuum. Also, the pressure in the predetermined tube is preferably vented after inspecting for air leakage.
To provide the second feature of an embodiment of the present invention, there is provided an apparatus for inspecting a polishing head for air leakage. The apparatus includes a housing operatively associated with an upper surface of the polishing head for supporting the polishing head, the housing having first, second and third coupling lines, the polishing head having first, second and third tubes, wherein each coupling line of the housing is independently communicated with a corresponding tube of the polishing head, a pneumatic pressure regulating section for selectively supplying a positive pressure or a vacuum to each of the tubes of the polishing head through the coupling lines of the housing, a sensor section for detecting, measuring and generating data relating to a level of positive pressure or vacuum in each of the tubes of the polishing head, and a determining section for receiving data relating to a level of positive pressure or vacuum in each of the tubes of the polishing head from the sensor section to ascertain whether air leakage exists in the polishing head by determining if the level of positive pressure or vacuum in each of the tubes of the polishing head is maintained over a predetermined period of time.
Preferably, the first, second and third tubes provided in the polishing head that are respectively communicated with the first, second and third coupling lines of the housing, are first, second and third air passages, respectively, and are respectively communicated with an inner tube, a membrane and a retainer ring of the polishing head. Also, the first air passage communicated with the inner tube preferably receives only positive pressure from the pneumatic pressure regulating section.
The pneumatic pressure regulating section preferably includes a main pressure regulating device for supplying positive pressure into the first, second and third tubes of the polishing head, a main vacuum regulating device for supplying vacuum into the second and third tubes of the polishing head, a first connection line connected to the main pressure regulating device for transferring positive pressure supplied from the main pressure regulating device, first, second and third pressure lines branched from the first connection line and connected respectively to the first, second and third coupling lines of the housing, each of the first, second and third pressure lines having a first valve for selectively opening and closing the first, second and third pressure lines, a second connection line connected to the main vacuum regulating device for transferring vacuum supplied from the main vacuum regulating device, first and second vacuum lines branched from the second connection line and connected respectively to the second and third coupling lines of the housing, each of the first and second vacuum lines having a second valve for selectively opening and closing the first and second vacuum lines, and a third connection line connected to the second coupling line of the housing, and connecting the second pressure line to the first vacuum line so that the second pressure line and the first vacuum line are connected to the second coupling line of the housing, and a fourth connection line connected to the third coupling line of the housing, and connecting the third pressure line to the second vacuum line so that the third pressure line and the second vacuum line are connected to the third coupling line of the housing.
Preferably, the first pressure line is directly connected to the first coupling line of the housing communicated with the inner tube of the housing.
The apparatus may further include a venting valve connected to each of the first valves and the first, second and third pressure lines to allow or prevent discharge of pressure from each of the tubes of the polishing head to an exterior.
Preferably, the sensor section includes first sensors provided on each of the first valves and the first, second and third pressure lines connected to the first, second and third coupling lines of the housing to detect pressure in the first, second and third tubes of the polishing head, and second sensors provided on each of the second valves and the first and second vacuum lines connected to the second and third coupling lines of the housing to detect a level of vacuum in the second and third tubes of the polishing head. Preferably, a timer is attached to each of the sensors of the sensor section for notifying of a lapse of time.
The apparatus may further include first control sections connected to the first sensors and the first valves for driving the first valves based on the data obtained from the first sensors in order to individually control pressure supplied to the first, second and third tubes of the polishing head, and second control sections connected to the second sensors and the second valves for driving the second valves based on the data obtained from the second sensors in order to individually control the vacuum supplied into the second and third tubes of the polishing head.
The apparatus may further include a driving section having a rail and coupled to a predetermined side portion of the housing for moving the housing and the polishing head supported by the housing in upward and downward directions along the rail, a motor connected to the housing for driving the housing along the rail, and a measuring section for measuring a driving distance of the housing.
There is preferably a seat sensor provided opposite to a bottom of the polishing head supported by the housing for detecting the pressure at each part of the bottom of the polishing head by making contact with the bottom of the polishing head, and a display section for displaying the pressure detected from each part of the seat sensor.
By using the assembling method and apparatus for a polishing head of the present invention, air leakage may be detected during assembly of the polishing head, unlike in the prior art, in which testing for air leakage is not performed until the polishing head is fully assembled and installed. If air leakage is detected during the process of assembling the polishing head in the present invention, the assembly step immediately prior to the detection of air leakage is repeated, and the leakage test is repeated, so that the polishing head may be assembled without any air leakage. Accordingly, by using the present invention, a lengthy test of the completely assembled and installed polishing head is unnecessary. In the prior art, if the polishing head is abnormally assembled and a leak is detected, all parts of the polishing head must be disassembled and re-assembled in order to stop the leak, a process that is eliminated by the present invention. Furthermore, when using the present invention, after assembling the polishing head, the polishing head may be installed in a polishing device and immediately used to polish a wafer, without having to be tested on a dummy wafer first, thereby improving the productivity of the semiconductor device manufacturing equipment.